European Patent No. 667 822 describes an air pressure detector which detects a side impact in a lateral part of a vehicle on the basis of a quasi-adiabatic increase in pressure. Acceleration sensors and/or structure-borne (noise) sensors are mentioned as plausibility sensors.
The device according to the present invention for side impact detection in a vehicle has the advantage over the related art that a plausibility check may also be performed on the basis of air pressure fluctuations in the lateral part of the vehicle, and therefore there is no delay in the plausibility check in comparison with a signal from a fast-acting impact sensor, e.g., a pressure sensor or a temperature sensor. Therefore, the restraint devices may be deployed more rapidly. In addition, this achieves an improved means of suppressing deployment of the restraint devices in harmless events such as a door being closed or some other impact on the lateral part. It is also possible to reduce costs through the device according to the present invention because plausibility sensors need no longer be mounted additionally, because the loudspeaker, which is located in the lateral part anyway for playback of music, for example, is used for the plausibility check.
It is particularly advantageous that a circuit for differentiating between sound and rapid fluctuations in air pressure may be connected to the loudspeaker, the circuit being connectable to a control device for the restraint devices. The circuit causes only air pressure fluctuations originating primarily from a side impact, i.e., from compression of the air pressure volume in the lateral part of the vehicle due to a penetrating object, to be taken into account, so it is impossible for other sounds such as music to falsify the measurement. This circuit permits in particular existing loudspeakers already present in the lateral parts of motor vehicles to be used for a plausibility check.
In addition, it is also advantageous that this circuit has a bridge circuit, the differential voltage across the bridge then being used as a plausibility signal.
Finally, it is also advantageous that the circuit in the door is preferably provided on the loudspeaker itself.